Innovative Post-Combustion CO2 Capture Process Into An Existing Coal-Fired Power Plant

An innovative solvent based, post-combustion, CO₂ capture process is currently in the detailed design phase for a 2 MW^th (0.7 MW^e) slipstream unit.  The process utilizes a two-stage stripper for solvent regeneration with water saturated air as the secondary stripping gas.    The gas stream exiting the top of the secondary air stripper will be recycled and used as boiler air, resulting in an increase of CO₂ concentration in the inlet gas stream 10-15% higher than baseline. This provides a higher driving force for CO₂ diffusion through the liquid/gas reaction film, and a higher mass transfer flux through increased the internal liquid circulation for a structured packed column.  High CO₂ concentration in the gas stream will increase the mass transfer flux, and increase the final carbon loading in the solution at the bottom of the absorber by approximately 17% over the value obtained without the enhanced CO₂ concentration.  This will also result in reduced stripper energy.

Additionally, this process includes a liquid desiccant loop providing moisture saturated air for the secondary stripper and dry air to reduce turbine cooling water temperature.  Finally, this process will be run with two solvents.  A baseline establishment study will be conducted using 30 wt% MEA solvent to obtain data for a direct comparison with the 2010 U.S. DOE National Energy Technology Bituminous Baseline Study’s Reference Case 10 (1).  Then, an advanced solvent from Hitachi will be included as part of the total performance evaluation.

A preliminary technical and economic analysis has been conducted on a commercial-scale version of the proposed process.  It includes a levelized cost of electricity (LCOE) assessment, for the proposed heat-integrated commercial-scale process. The key factors contributing to the reduction of LCOE were identified as CO₂ partial pressure increase at the flue gas inlet, thermal integration of the CO₂ capture process with the power plant to improve steam turbine efficiency and the performance of the advanced solvent.  The UKy-CAER CCS process MEA case lowers energy consumption for CO₂ capture to 1340 Btu/lb-CO₂ captured as compared to 1540 Btu/lb-CO₂ (1). The study also shows 38.1% less heat rejection associated with the carbon capture system from 3398 MBtu/hr (1) to 2104 MBtu/hr for the UKy CAER system.

Upon successful completion of this project, the next step would be to scale to 15-25 MW^th.  Potential interested parties, both in the United States and China, have already been identified to host such a project.

(1)  DOE, Cost and Performance Baseline For Fossil Energy Plants, Volume 1: Bituminous Coal and Natural Gas to Electricity, Revision 2, 2010.